Interleukin-23 (IL-23) is the name given to a factor that is composed of the p40 subunit of IL-12 (IL-12beta, IL-12-p40) and another protein of 19 kDa, designated p19. p19 is structurally related to IL6, G-CSF, and the p35 subunit of IL-12. Like IL-12 p35, IL-23 p19 cannot be secreted as a monomer and has not demonstrated biological function. Rather, each subunit must partner with p40 to be expressed by antigen presenting cells (APC) and mediate biologic effects. The active complex is secreted by dendritic cells after cell activation. Mouse memory T-cells (CD4 (+)CD45 Rb(low)) proliferate in response to IL-23 but not in response to IL-12. Human IL23 has been shown to stimulate the production of IFN-gamma by PHA blast T-cells and memory T-cells. It also induces proliferation of both cell types. Human monocyte-derived macrophages produce IL23 in response to virus infection (Sendai virus but not Influenza A virus).
IL-23 binds to the beta-1 subunit but not to the beta-2 subunit of the IL-12 receptor, activating one of the STAT proteins, STAT-4, in PHA blast T-cells. The IL-23 receptor consists of a receptor chain, termed IL-23R, and the beta-1 subunit of the IL-12 receptor. The human IL-23R gene is on human chromosome 1 within 150 kb of the gene encoding IL-12Rbeta2. IL-23 activates the same signaling molecules as IL-12: JAK2, Tyk2, and STAT-1, STAT-3, STAT-4, and STAT-5. STAT-4 activation is substantially weaker and different DNA-binding STAT complexes form in response to IL-23 compared with IL-12. IL-23R associates constitutively with JAK2 and in a ligand-dependent manner with STAT-3.
Expression of p19 in transgenic mice leads to runting, systemic inflammation, infertility, and death before 3 months of age. The animals show high serum concentrations of the pro-inflammatory cytokines TNF-alpha and IL1. The number of circulating neutrophils is increased. Acute phase proteins are expressed constitutively. Animals expressing p19 specifically in the liver do not show these abnormalities. Expression of p19 is most likely due to hematopoietic cells as bone marrow transplantation of cells expressing p19 causes the same phenotype as that observed in the transgenic animals.
Biologically active IL-12 exists as a heterodimer comprised of 2 covalently linked subunits of 35 (p35) and 40 (p40) kD. IL-12 acts by binding to both the IL-12beta 1 and beta 2 receptor proteins and thereby induces signaling in a cell presenting both of these receptors. Several lines of evidence have demonstrated that IL-12 can induce robust Th1 immune responses that are characterized by production of IFNγ and IL-2 from CD4+ T cells.
IL-12 is produced by APCs in response to a variety of pathogens. One example is the protozoan parasite Leishmania major, which has been used as an in vivo model for defining factors involved in T cell development. Resistant strains of mice developed Th1 responses characterized by robust IFNγ production. In contrast, susceptible mice demonstrate a Th2 cytokine profile most often described by IL-4, IL-5, and IL-10 production. It was shown that IL-12 could restore immune function in susceptible mice and administration of a neutralizing anti-p40 antibody resulted in disease onset in otherwise resistant strains. This change in disease susceptibility was associated with a reversal of T cell cytokine profiles. Therefore, IL-12 has been identified as a critical parameter in defining Th1 differentiation.
Inappropriate Th1 responses, and thus IL-12 expression, are believed to correlate with many immune-mediated inflammatory diseases and disorders, such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, insulin-dependent diabetes mellitus, and uveitis. In animal models, IL-12 neutralization through its p40 subunit was shown to ameliorate immune-mediated inflammatory diseases. For example, administration of recombinant IL-12 exacerbated EAE, and treatment with neutralizing anti-p40 antibodies inhibited EAE onset or relapses. In addition, IL-12 p40−/− mice are completely resistant to EAE even though mice deficient in other pro-inflammatory cytokines, such as IFNγ, TNFα, or LTα, remain susceptible. IL-12 p35−/− mice are fully susceptible to EAE, which suggests that alternative p40 cytokines, such as IL-23, are responsible for such diseases. The role of IL-23 in EAE and collagen-induced arthritis (CIA) has been recently confirmed in studies using p19−/− mice. These animals demonstrated complete resistance to disease induction, similar to p40−/− mice.
Non-human, chimeric, polyclonal (e.g., anti-sera) and/or monoclonal antibodies (Mabs) and fragments (e.g., proteolytic digestion products thereof) are potential therapeutic agents that are being developed in some cases to attempt to treat certain diseases. However, such antibodies that comprise non-human portions elicit an immune response when administered to humans. Such an immune response can result in an immune complex-mediated clearance of the antibodies from the circulation, and make repeated administration unsuitable for therapy, thereby reducing the therapeutic benefit to the patient and limiting the readministration of the Ig derived protein. For example, repeated administration of antibodies comprising non-human portions can lead to serum sickness and/or anaphalaxis. In order to avoid these and other such problems, a number of approaches have been taken to reduce the immunogenicity of such antibodies and portions thereof, including chimerization and “humanization,” as well known in the art. These approaches have produced antibodies having reduced immunogenicity, but with other less disirable properties.
Accordingly, there is a need to provide anti-IL-23p40 antibodies or specified portions or variants, nucleic acids, host cells, compositions, and methods of making and using thereof, that overcome one more of these problems.